Radar data is frequenty old or missing

Have been experimenting with using the API calls for radar data. I have a vb program running that makes the API call every 10 minutes and place the image in a web browser. While the map background and time stamps are correct very often the radar image is old (several weeks) and then it will be correct again for a few and then the old data or just no data is displayed. Other radar sites NWS WXtap ect. have the correct data at the time WU is failing..